1. We review a workers compensation award in the light most favorable to the prevailing
party to determine whether the Board's findings are supported by substantial
competent evidence. Substantial competent evidence possesses something of substance
and relevant consequence or furnishes a substantial basis in fact from which issues can
reasonably be resolved. We will not reweigh evidence or evaluate the credibility of
witnesses.

3. When a work-related event causes aggravation of a preexisting condition, the
employee is entitled to compensation for any increase in the amount of functional
impairment. The test is not whether the job-related activity or injury caused the
condition but whether the job-related activity or injury aggravated or accelerated the
condition.

4. A preexisting condition is distinct from a preexisting disability. When there is no
evidence of the amount of preexisting disability or impairment due to a preexisting
condition, there is nothing to deduct from the total impairment to ensure that the
employer and/or its carrier are excused from covering the preexisting portion.

5. The burden of proving a workers compensation claimant's amount of preexisting
impairment as a deduction from total impairment belongs to the employer and/or its
carrier once the claimant has come forward with evidence of aggravation or
acceleration of a preexisting condition.

Russell B. Cranmer, of affiliated attorneys of Pistotnik Law Office, of
Wichita, for appellee.

Before BEIER, P.J., ELLIOTT, J. , and FRED S. JACKSON, S.J.

BEIER, J.: This appeal by the respondent-appellant school district and its insurance
carrier seeks reversal of a workers compensation award to claimant-appellee Kenneth Hanson
for permanent impairment of the function of his right knee. We affirm.

Hanson, who coached track for respondent Logan U.S.D. 326, claimed he injured his
knee on May 19, 1995, while unloading supplies at a track meet. Hanson said that his knee
popped when he stepped down from a school bus, that he immediately had trouble walking,
and that he had swelling and other problems thereafter.

Hanson did not seek treatment for his knee until July 19, 1995. Dr. Gary Harbin,
who had performed arthroscopic surgery on the knee in 1989, performed another surgery in
August 1995. He removed a bone spur and observed moderately advanced arthritis and
bone-on-bone contact consistent with his 1989 observations. Harbin testified that Hanson would
have ultimately needed a knee replacement but that the work-related injury could have
accelerated the need. Hanson experienced less pain and improved mobility after the bone
spur surgery.

Hanson returned to work in the fall of 1995 and continued to coach. He saw Dr.
Gregory Woods in February 1996, complaining of stiffness and difficulty straightening his
knee and an achy, nonspecific pain. X-rays showed severe degenerative arthritis with bone
rubbing on bone. Woods considered the complaints consistent with the degenerative
condition, possibly exacerbated by the May 19, 1995, injury. He said Hanson would have
had "a fair degree of impairment" before the work-related injury, but he could not judge how
much because he had not seen him at that time. Woods recommended a knee replacement to
relieve Hanson's pain. Hanson underwent knee replacement surgery in June 1996.

The administrative law judge (ALJ) ordered an independent medical examination by
Dr. Kenneth Jansson. In Jansson's opinion, Hanson's waxing and waning of symptoms after
the work-related injury were more consistent with a chronic condition than with an acute
injury. Jansson assigned an impairment rating of 10 percent because of Hanson's pain. He
attributed 95 percent of the impairment to the preexisting condition.

Based upon an examination of Hanson, his medical history, and his records, Dr.
Daniel Zimmerman testified that, in his opinion, the May 1995 incident permanently
aggravated the preexisting degenerative change in Hanson's knee. He rated Hanson's
impairment of function at 41 percent after Hanson underwent a knee replacement. He
believed Hanson would have had some impairment of function prior to the work-related
injury but could not quantify it.

The ALJ found that Hanson suffered a personal injury by accident arising out of and
in the course of his employment that accelerated his need for knee replacement surgery. The
ALJ also found that Hanson suffered a 33.67 percent permanent partial disability of the right
lower extremity. The Board modified the award to a 41 percent loss of use.

The parties do not dispute that, before his alleged work-related injury, Hanson had
had several knee surgeries and suffered from a degenerative condition that would ultimately
necessitate a total knee replacement. Respondent questions whether Hanson actually
experienced injury on the date and under the circumstances alleged, and whether the amount
of impairment attributed to the injury's aggravation of his preexisting disability is correct.

The finding that Hanson suffered an accidental injury in the course of his
employment on May 19, 1995, is supported by substantial competent evidence. Hanson
testified that he felt his knee pop and that he had immediate pain and swelling. A claimant's
testimony alone is sufficient evidence of his own physical condition. See Graff v. Trans
World Airlines, 267 Kan. 854, 863-64, 983 P.2d 258 (1999). Although respondent makes
a
compelling argument regarding Hanson's delay in seeking medical treatment, Dr. Harbin's
testimony supports his patient's position. Harbin testified that Hanson's history subsequent
to the alleged injury was consistent with an aggravation of his condition. We are not free to
substitute our judgment of the credibility of the witnesses.

With regard to the amount of impairment attributed to the work-related injury's
aggravation of Hanson's preexisting disability, we turn first to Woodward. In that
case, the
employee experienced aggravation of preexisting severe degenerative changes in his right knee
as a result of an on-the-job injury to his left knee. Considering evidence that the knee would
degenerate regardless of subsequent injury and that the injury could only hasten the process,
the Board found that the aggravation of the right knee was compensable as a direct and
natural result of the work-related injury to the left knee. 24 Kan. App. 2d at 512-13. This
court affirmed the Board's functional disability award for a bilateral injury, noting that the
test is not whether the job-related activity or injury caused the condition but whether the
job-related activity or injury aggravated or accelerated the condition. 24 Kan. App. 2d at 514.

When a work-related event causes aggravation of a preexisting condition, the
employee is entitled to compensation for an increase in the amount of functional impairment.
The controlling statute provides:

"The employee shall not be entitled to recover for the aggravation of a preexisting
condition, except to the extent that the work-related injury causes increased disability. Any
award of compensation shall be reduced by the amount of functional impairment determined
to be preexisting." K.S.A. 1999 Supp. 44-501(c).

The statute clearly distinguishes between a preexisting condition and a preexisting
disability. There is no evidence of the amount of Hanson's preexisting disability, and there is
some evidence that Hanson had no impairment prior to the May 19, 1995, injury. Hanson
had not sought treatment for his knee from Dr. Harbin since the 1989 surgery, and Hanson
testified his activities were not restricted because of his knee until after the May 1995 injury.
There was no amount of impairment for the Board to deduct from the total impairment to
ensure that respondent was excused from covering the preexisting portion.

We agree with Hanson that the burden of proving his preexisting impairment as a
deduction from total impairment belonged to respondent once Hanson had come forward
with evidence of aggravation. We think this type of burden shifting pattern is implicit in
Woodward's holding that, where a work-related injury causes aggravation or
acceleration of a
preexisting condition, compensation is allowed for the entire disability without
apportionment of causation. 24 Kan. App. 2d at 514. Hence, the claimant need only show
aggravation or acceleration of the condition and a causal relationship between the work-related
injury and the disability. Once the claimant shows increased disability, compensation
is for the full amount of disability less any amount of preexisting impairment established by
the respondent. This is also pragmatic. Only the respondent has an interest in establishing
the amount of preexisting impairment, and the respondent would be as foolish to rely on the
claimant to prove it as the claimant would be to do so.

Because the record lacked any evidence of the amount of preexisting disability or
impairment, the Board had no choice but to deduct zero from the total.